like my new avatar?

[ph2t]

I think it’s fitting given my reputation in the FET community, lol….

ph2t.

[z-beam]

wtf is it man? looks like a burnt up bcg chassis…

[brendan]

his burnt fets from his monster me thinks:approve:

[ph2t]

Yerp:

They smell worse then they look too……….

ph2t.

[betty.k]

crikey!!!:8ball:

[micro_Amps]

Man !! Talk about toast.:shock:
Must be giving it a real hard time.
What are you running?
:)uA

[ph2t]

well the last frying episode was an attempt at 6 cells…… I dunno what happened something must of short ’cause as soon as I turned the power on (no motor in cct) the fets started to fry….

Some things I have found out though:

1) The circuit is always on with respect to the drivetrain h-bridge & steering h-bridge. The Source pins on the p-chan fets in both h-bridges are connected directly to Vcc.

2) The battery Vcc rail is switched AFTER the connection to the two h-bridges. Therefore the whole circuit turns off except for the p-chan fets in both h-bridges. (this makes sense since my first fet frying incident continued to fry even after turning the power switch off)

3) Once fets overheat they short out. So even if you keep turning the PCB off and let it cool, you’re still gonna have problems…..

4) I believe that the safest way to do a 6 cell mod is to use a 5V regulator (or a LM317T to regulate at 4.8V for those anal techies out there….. :)) and just power the main circuit with this. I think one should power the steering this way as well jsut to be safe. That requires you to cut the PCB track going to the Source pins on the p-chan fets in the steering h-bridge to isolate them from the drivetrain h-bridge…..

My heads gonna burst, gotta get back to making my madforce just work!

ph2t.

[micro_Amps]

Quote:

The circuit is always on with respect to the drivetrain h-bridge & steering h-bridge. The Source pins on the p-chan fets in both h-bridges are connected directly to Vcc.

This is standard, the fets form part of the onboard ESC circiut, you will probably find that the (-ve) is connected directly to the N chan fets as well.
If you think of it as a 1/10 scale car, the batteries go to the ESC, and the motor goes to the ESC, the servo control wire just governs how much it is turned on, and the switch only switches the controlls not the ESC.
If the ‘on/off’ switch switched all the power to the car it would also be switching the large motor current as well, and the switch would have to be large and heavy. Essentially the ESC is ‘the switch’.
If the car is starting to heat up (or fry) go straight for the batteries and remove them. As soon as you remove the first one the circuit will be open, and the frying should stop.

So now you know for the next time, because I know there will be a next time.:smiley2:
:)uA

Edited by – micro_Amps on 11 April 2004 08:15:02

[ph2t]

Now that you explain it that way dude, it make perfect sense…..

Hopefully there won’t be next time……..

ph2t.

[jamiekulhanek]

6 cell mod requires no regulator. I have been looking into separate motor/rx batteries

[Author]

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